In the vehicle seat described in Japanese Patent Application Laid-Open (JP-A) No. 2008-238969, a seating portion is provided, and a seatback is coupled to the seating portion. The seatback includes a lower portion frame, and a first pin and a second pin are provided to the lower portion frame. The seatback includes side frames, and a first through hole and a second through hole are formed to each of the side frames. An auxiliary hole portion is in communication with the second through hole, and the auxiliary hole portion is open to the second through hole side. The side frames are coupled to the lower portion frame by inserting the first pin through the first through hole, and inserting the second pin through the second through hole.
However, when an impact load is imparted to the seatback in the vehicle rear direction, the side frames rotate centered on the first pin, and an edge portion of the second through hole abuts the second pin at two connection portions of the second through hole and the auxiliary hole portion. The auxiliary hole portion deforms by being pressed to be widened by the second pin. The impact energy imparted to the seatback is thereby used to deform the auxiliary hole portion, enabling the impact load imparted to the seatback to be absorbed.
Moreover, the automobile seat described in JP-A No. 2010-500213 is equipped with a seat portion structure. An adapter is coupled to the seat portion structure by a pivot and fixing screw, and a backrest structure is coupled to the adapter.
A hole is provided in the adapter into which the fixing screw is inserted. Cutout portion are formed at a side portion of this hole so as to pierce through at specific intervals, with a connection portion configured between the hole and the cutout portion, and between one cutout portion and the other cutout portion.
However, when an impact load is imparted to the backrest structure in the vehicle rear direction, the adapter rotates about the pivot, the connection portion between the hole and the cutout portion makes contact with the fixing screw and is broken (deformed). When the connection portion was broken, the broken connection portion then makes contact with the next connection portion between one cutout portion and another cutout portion. The impact energy imparted to the backrest structure is used as energy to break (deform) each of the connection portions, thereby enabling the impact load imparted to the backrest structure to be absorbed.